This invention relates to a machine and a method for applying a liquid coating to a surface, such as a floor, and more particularly to such a machine and method whereby liquid may be applied to a surface, such as a floor, in a generally continuous and progressive manner and at a substantially constant rate to form a generally uniform coating thereon.
Known methods for applying wax and other liquid coatings to hard floors, carpeting, or the like have generally involved applying the liquid, such as wax, sealer, fabric protection solution, etc., manually, such as with a mop or with a manually operated pump-type sprayer. Such manual methods have many disadvantages. Perhaps the biggest such disadvantage is that it is generally very difficult to apply a liquid coating uniformly to a floor surface using manual application techniques. For example, with a mop, the liquid is initially applied to the floor in the form of a thick layer or puddle, either by using the mop or by pouring the liquid directly onto the floor. The thick layer or puddle is then spread around using the mop. The thickness and uniformity of the resulting coating is very much dependent upon the skill, experience, and care of the particular worker.
It is also difficult to apply a uniform liquid coating to a floor using manual pump sprayers. Manual pump sprayers used for applying a liquid coating to a floor are generally comprised of a large canister-like container for the liquid and a manual pump mounted on the container which is used to deliver pressurized air to the space in the container above the liquid to cause the liquid to discharge through a nozzle under pressure when a manually operated valve is opened. One such device includes a pressure vessel which can be strapped to the back of a worker, and a hand-held spray wand with flexible tubing connecting the vessel with one end of the wand. The wand includes a nozzle at its free end, and a trigger-operated valve to allow pressurized liquid to flow through the nozzle. As with the mop application technique, the uniformity of the liquid coating so applied is very dependent upon the skill, experience, and care of the worker applying the coating.
A major problem that the worker has in applying a uniform coating with such a device is that the rate at which liquid is discharged from the nozzle constantly changes because the pressure in the space above the liquid constantly decreases as the liquid is discharged. In addition to the non-uniform rate at which the liquid is discharged from the nozzle, the uniformity of the spray pattern generally deteriorates as the pressure in the space above the liquid in the vessel decreases, i.e., the quantity of liquid applied to a surface generally becomes much greater near the center of the discharge pattern than near the periphery as the pressure forcing the liquid through the nozzle decreases. Another disadvantage with manual pump-type devices is that they have a relatively limited capacity and must be frequently refilled and repumped. Because of this, and because the devices are carried by the worker, such as on the back of the worker, the manual pump-type floor coating devices are extremely cumbersome and poorly suited for treating large surface areas, such as in office buildings, factories, airports, etc.
Another type of applicator which has been used for applying liquid coatings to floors includes an apparatus having a large liquid reservoir mounted on a wheeled cart above a lamb's--wool pad or a mop. The liquid is released by way of a valve which when opened allows the liquid to flow under the influence of gravity into a perforated manifold and through the perforations in the manifold to the floor below. Such a device supplies the liquid to the floor as a series of small streams and relies upon the pad or mop to spread the liquid over the floor. The result is a relatively non-uniform, streaky coating.
A still further type of applicator includes a frame, mounted on wheels, for supporting a liquid-storage tank that has a pressure feed mechanism for applying pressure to the liquid storage tank and delivering liquid to one or more selectively operable nozzles. Notably, the pressure feed mechanism of this known device dispense the liquid at a relatively low pressure, such that a stream, as opposed to a spray, of liquid is applied to the floor. The resulting rivulets of liquid must thereafter be spread by a mop-type finish spreader in order to cover the entire width of the machine being used. Similar to the other devices described above, the result is a heavy, non-uniform, streaky coating.
In addition, by dispensing the product as a low-pressure stream, the resulting relatively thick coating of material applied to the floor takes a significantly longer time to cure than a lighter coat, does not cure properly, and is usually cloudy and unattractive as well as remaining somewhat soft and non-durable. Furthermore, one coat is rarely sufficient to satisfactorily complete the job, and additional coats cannot be applied until the previously applied coat cures. As those skilled in applying floor coatings will appreciate, a series of well-cured light coats of finishing material is significantly more durable than applying one or more heavier coats. Therefore, the field of floor coating machines is in need of an apparatus that can efficiently spray finishing material as a continuous, generally uniform, thin coat such that streaking and pooling of the dispensed product, which typically results from applying thick coats of material, is avoided.